UPDATE 9:23AM: The wind chill advisory that was issued for some of Chicago’s western suburbs was allowed to expire at 9AM.
While the wind chill numbers are no longer in the “advisory” catagory (-20 to -30), a strengthening southwest wind will limit any improvement in the index to between zero and 5 degrees above zero.
A wind chill advisory is in effect until 9AM for McHenry, Kane, De Kalb, Kendall and Grundy Counties.
A wind chill advisory is issued when the wind chill index drops below -20 degrees.
At -20 to -30 degrees, exposed skin can freeze within minutes, possibly leading to frostbite.
Thanks to Ann Roos of Schaumburg for sharing these shots of icicles that have become so common around the Chicago area in recent days.
Photos by Ann Roos
Chicago has endured a prolonged cold spell and the city’s temperatures have not been above freezing since the thermometer hit 43 degrees on Christmas Day. That was 16 days ago, and the city area has also had 14 to 20 inches of snow during that cold period. After widespread subzero readings early this morning in the coldest outlying locations, daytime temperatures, aided by abundant sunshine, are set to recover rapidly to the middle and upper 20s in the afternoon. A short-lived but nonetheless potent reinforcing surge of Canadian air arrives early Monday, accompanied by a dusting of snow.
Cold pattern breaks; warmer days ahead
All cold things must come to an end, and computer models of the atmosphere indicate Chicago’s lengthy cold spell has just about run its course. A relatively mild flow of Pacific air is heading this way and should arrive Wednesday. The city’s string of days with temperatures at or below freezing will end at 18 on Tuesday as readings on Wednesday surge well into the 30s. And that’s the start of a new pattern of “mild” days.
What is the farthest south “polar expresses” have driven?
-Vic Mazylewski, Shorewood
Arctic outbreaks routinely penetrate into the Deep South and a few will sweep through Florida and Texas. However, some cold surges have reached Central America and the northern portion of South America. Topography plays a limiting role, with Central American mountain ranges halting the southern push of cold air. Some of the natural barriers include the Sierra Madre range and the Costa Rican mountains south of Lake Nicaragua. Afew vigorous cold outbreaks have made it to about 7 or 8 degrees north latitude where they were finally halted by the mountains of Colombia. At those low latitudes, the cold air is very shallow and greatly modified, and only lowers the temperature a few degrees.
Lake effect snow could take another swipe at Illinois shoreline communities today, including downtown Chicago and portions of the city. While little or no accumulation is expected, the return of some flurries or snow showers may come as a bit of a surprise to many.
Surface winds out of the northwest are battling northeast winds aloft. The northeast winds may overcome the surface flow at times, allowing for some lake effect snow showers to return to Illinois.
Northwest Indiana will remain the most favorable area for lake effect snow today. As of 7AM, Warnings are still posted for Porter and LaPorte Counties, but some accumulation may occur as far west as Lake County, Indiana.
Lake Michigan may be the culprit at times for additional snow across the Chicago area, but it also spares many from the worst of an arctic outbreak.
There was an impressive 40 degree temperature swing across northern Illinois and northwest Indiana this morning. The low this morning in Rock Falls, IL plummeted to -18 F, while the temperature at Burns Harbor, Indiana did not fall below 20 degrees, on the positive side of zero. The low at the Chicago Lakefront was 16F.
The main reason for the warmer temperatures: The mainly unfrozen waters of Lake Michigan that vary anywhere from 32 to 38 degrees above zero.
Here are some of the area lows on this Saturday morning:
-18 Rock Falls/Sterling, IL
-18 Rochelle, IL
-11 Lacon, IL
-8 Kankakee, IL
-5 DeKalb, IL
-3 Minooka, IL
+6 Chicago (O’Hare)
+9 Chicago (Midway)
+16 Chicago Lakefront (Northerly Island)
+20 Michigan City, Indiana
+22 Burns Harbor, Indiana (Porter County)